`foreign-state`

Node code reaches another node's state.

compile error, shown by synod check.

In node code, state is reached only through the receiver of the define or when that contains the code. Any other node value gives identity only. Other nodes learn through net.Send. The same error covers a node other than the receiver after from, on or by.

Example

Check this program to see the diagnostic.

# package p
Node has
  set count to 0

define [n: Node] Copy from [peer: Node]
  set n.count to peer.count

Diagnostic

p/p.synod:6:18: error[foreign-state]: node code reaches "peer.count" through "peer", not its receiver "n"
  hint: other nodes learn through net.Send

Fix

Take the value as a hole. A real peer would send it in a message with `net.Send`.

# package p
Node has
  set count to 0

define [n: Node] Take [c: number]
  set n.count to c